A B-52 carries an X-51 hypersonic demonstrator for a test launch in May, when the vehicle reached speeds over Mach 5. (Bobbi Zapka / Air Force)

For much of the past decade, the buzzword A2/AD — anti-access/area-denial — has been closely linked with stealth technology. But with many nations slowly developing their own stealth capabilities, the Air Force is looking for new advantages it can create to counter a foe’s A2/AD threats.

“The US enjoys several tremendous advantages, including space and stealth technologies,” said Mark Lewis, former Air Force chief scientist. “So what comes after stealth? I’d argue part of the answer is speed.”

Stealth technology is based on a simple concept: If the enemy doesn’t know you are there, he can’t stop you. Speed, Lewis argues, takes that calculus and turns it on its side. A platform or weapon coming in at extremely high speeds will likely light up a radar system, but it’s also coming so fast that an enemy will not be able to react in time.

The Air Force is researching how weapons can take advantage of speed in future A2/AD conflicts through platforms such as the Boeing-designed X-51 WaveRider hypersonic demonstration vehicle. A booster accelerates the missile to over Mach 4, at which point the booster separates and a scramjet engine takes over, theoretically reaching speeds upwards of Mach 6 — about 4,000 miles per hour. A Tomahawk cruise missile, by comparison, travels about 550 miles per hour.

The X-51 is designed to release off the wing of a B-52, but future versions could eventually fit into the bay of an F-22 — or the new in-development long-range bomber. At around 4,000 pounds and with a range of 400 nautical miles, a weapon based on the X-51 should ideally bring a mix of range and speed that could be incredibly useful against an enemy’s A2/AD systems — assuming it works. Out of four active tests of the missile, two failed and two succeeded, most recently in May, when an X-51 flew for several minutes at Mach 5.1.

While high-speed weapons may be the future, they are unlikely to replace stealth technology.

“I don’t think of it as versus stealth; I think of it as in-addition-to stealth,” Lewis said. “You want to have a mix of capabilities. That’s the direction I think the Air Force will ultimately be moving towards.”

Speed and stealth can serve two different missions, argues James Acton, senior associate with the Carnegie Endowment for International Peace’s Nuclear Policy program.

“I don’t know if in 20-30 years stealth or speed will be the best way to penetrate defenses,” he said during a Sept. 3 speech. “But I do think it is a critical issue that needs to be taken [into] account.”

“At a time when there was a lot more money available, it was OK to say all forms of solving the problem should be investigated,” he added. “At a time of fiscal austerity, I think it’s important to prioritize the option that carries the least risk of failing to fulfill military goals. The question is comparing risk.”

Global Strike Capability

Acton is the author of a major study on the Conventional Prompt Global Strike (CPGS) family of systems, which could provide another option for countering A2/AD systems.

A long-range, non-nuclear weapon capable of quickly striking anywhere in the globe, CPGS is simple in concept but technically difficult in practice. CPGS has been in development since 2003, but the program has finally matured enough that its use should be viable by the early 2020s.

Theoretically, CPGS could be perfect for a strike aimed at crippling the A2/AD capabilities of an enemy nation, in particular a large country such as China. Given their cost and limited number, CPGS weapons would likely not be used to take out anti-aircraft batteries when something more simple, such as a Tomahawk missile, would do. It would also not be as useful against mobile targets.

Instead, CPGS could be used to destroy key sites, such as command-and-control centers that form the hub of integrated defense systems.

“Long-range missiles are part of the long-range strike family of systems, but may not be the best weapons to use against mobile/movable targets such as missile TELs [transporter erector launchers], or hardened/deeply buried targets. Plus, they tend to be costly,” Mark Gunzinger, an analyst with the Center for Strategic and Budgetary Assessments who served in a number of Pentagon roles, wrote in an email.

“For limited strikes against appropriate targets, they may be the weapon of choice,” he added. “For a serious air campaign in A2AD conditions, survivable, penetrating strike systems as well as standoff attack missiles are needed.”

That last point is key when shaping the Air Force’s counter-A2/AD future. It is unlikely to come from one specific magic technology. Instead, the service will likely need a range of technologies capable of adapting to a variety of situations.

“Different missions have different requirements, and that’s the place where a strategic acquisitions process should begin,” Acton said.

He added that before the Pentagon commits to any new weapons systems, it needs to undergo a full study looking at how they would operate under a number of potential threat scenarios.